(a) Field of the Invention
The invention concerns a process for the gas treatment of a product in a confined treatment zone.
(b) Description of Prior Art
An example of such a treatment is the deoxygenation of a nutritious liquid. As a matter of fact, in this type of applications, the presence of oxygen often limits the time of preservation of the products since oxygen produces phenomenona of aerobic fermentation, or phenomena of oxidation of the components which are responsible for the modification of the organoleptic properties of the product (aroma, taste). Now, all the nutritious liquids contain dissolved oxygen when they are placed in contact with ambient air, the quantity of dissolved oxygen being proportional to the partial pressure of oxygen at the surface of the liquid, and varies as a function of temperature, pressure and composition of the liquid.
Therefore, to avoid these phenomenona, the liquids which take part in food processing are currently treated:
either by deoxygenation of water used for diluting beer manufactured by the so-called high density process, PA1 or by deoxygenation of fruit juices. PA1 heating PA1 vacuum PA1 "stripping" with nitrogen or carbon dioxide
Deoxygenation generally relies on one of the three following technical steps:
which are used alone or in combination, in order to achieve a final dissolved oxygen content which is lower than or equal to 0.05 mg/l at 10.degree. C.
According to this technique of "stripping", a deoxygenating inert gas (nitrogen, carbon dioxide) is injected under pressure by means of injectors or ejectors into a liquid to be deoxygenated. Contact between inert gas and liquid is promoted either by a minimum length of contact duct in the first case, or by a Venturi system in the second case.
Thus, oxygen is displaced by means of dissolved nitrogen or carbon dioxide, and the mixture of O.sub.2 and inert gas passes off during the decantation phase which takes place in a vat at atmospheric pressure. The process thus comprises one or two steps of injection enabling achieving the desired content of dissolved oxygen, which is 0.05 mg/l.
In the case of equipment operating in two steps, the consumption of nitrogen is 3.4 cubic meter of gas per cubic meter of liquid treated to go from 10 mg to 0.05 mg of dissolved oxygen per liter of treated liquid.
Although "stripping" with nitrogen gives excellent technical results, this procedure is economically uncompetitive with other techniques in particular deoxygenation under vacuum, since nitrogen consumption is quite high.